Laser powder bed fusion of NiTi ternary alloys: a review

NiTi-based shape memory alloys (SMAs) have attracted significant attention due to their ability to recover large strains and their unique functional properties. Their high corrosion resistance, excellent ductility, and strong work-hardening behaviour make them suitable for specialised applications. However, conventional processing methods are challenging and often restrict components to simple geometries. Laser powder bed fusion (LPBF) enables the fabrication of complex structures while allowing precise control over alloy chemistry and microstructure. Over the past decade, research has focused on optimising scanning parameters and understanding the thermoelastic behaviour of binary NiTi, though results remain highly sensitive to feedstock and processing variations. To further enhance performance, alloying with ternary elements such as Hf, Cu, Nb, and Fe has been explored. This review highlights recent advancements in LPBF-fabricated NiTi-X alloys, focusing on printability, microstructure, and functional evolution. Hf addition improves functionality, achieving martensite start temperatures up to 300 °C. Nb enhances mechanical properties, including yield strength and plateau strain, while Cu improves phase stability and thermal cycling capability. Overall, this review contributes to a deeper understanding of LPBF-processed NiTi-X alloys, helping unlock their potential for high-performance applications.